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Using egg leftovers could double the number collected in IVF

Don’t waste the scraps

CC Studio/Science Photo Library

By Jessica Hamzelou

COULD this be a way to make more eggs? A technique that uses their genetic leftovers could double the number collected in IVF.

In a typical IVF treatment, a woman takes drugs to stimulate more eggs to mature and be released than normal. A doctor then surgically removes the eggs and fertilises them in the lab. The healthiest embryos are then implanted in the uterus in the hope they will develop into a fetus.

To be successful, it helps to have lots of eggs in the first place. With drugs, most women can produce around 10 to 15. But older women or those with a low egg reserve release much fewer, meaning they may need more rounds of IVF treatment to get pregnant.

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Now Shoukhrat Mitalipov at Oregon Health and Science University in Portland and his colleagues have found a way to increase the number of eggs. In the two cell divisions that create an egg, three other tiny cells are also produced. These are known as polar bodies and eventually degrade, but they each contain all the DNA a normal developing egg would have, prompting Mitalipov to wonder whether this could be put to good use.

His team collected eggs from 11 volunteers using the standard IVF approach, which involves collecting eggs just as the first polar body forms. Instead of discarding the polar body, the researchers placed it alongside an egg donated by another individual that had its DNA-containing nucleus removed. These eggs were able to incorporate the polar body, which seemed to replace the missing nucleus.

This meant each woman had a set of her own eggs, plus donor ones carrying her DNA in their nuclei. The eggs were then fertilised using sperm from a donor. “Most of the resulting embryos look very normal,” says Mitalipov, who subjected them to rounds of genetic and epigenetic testing to screen for any signs of unusual development (Cell Stem Cell, doi.org/bs2c).

Although the technique could in theory double the number of eggs produced in IVF, at the moment Mitalipov reckons it could increase the number by 50 per cent. “That is actually huge for IVF,” he says. “Around 60 per cent of IVF patients have infertility due to age. The number of eggs these women have declines.”

The procedure has benefits and drawbacks, says Bert Smeets at Maastricht University in the Netherlands. “It’s nice that they are able to reuse the material [from the polar body], but you still need a donor egg,” he says.

He points out that the extra eggs also have donor DNA in their mitochondria – small bodies that generate power for the cell. This probably communicates with nuclear DNA, and we don’t know whether having DNA from two different sources will cause any problems later in life, he says. “The simpler thing to do would be to have children younger, or freeze your eggs at a younger age,” says Smeets.

The technique would have to be approved before it can be offered in fertility clinics, but it looks safe, says Jacob Hanna at the Weizmann Institute of Science in Rehovot, Israel. “There are no red flags or scary signs,” he says. “It looks as safe as possible.”

This article appeared in print under the headline “IVF eggs from leftover DNA”